Sectional parabolic reflector



Nov. 24, 1970 H. A. PAYNE SECTIONAL PARABOLIC REFLECTOR Filed July 18, 1968 IN VENT OR. HAROLD A. PAYNE yawa /f4.

ATTORNEYS United States Patent 3,543,278 SECTIONAL PARABOLIC REFLECTOR Harold A. Payne, 252 Bering Ave., Toronto 18, Ontario, Canada Filed July 18, 1968, Ser. No. 745,809 Int. Cl. H01q 15/20 US. Cl. 343-915 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to a parabolic reflector of the type used in the communication field where there is a need to pick up communication signals and feed them into an antenna head or communication network.

Reflectors of this type are used in radar systems and microwave telecommunication systems.

A commonly used parabolic reflector is one made from smooth aluminum sheets spun into the shape of a parabola. These reflectors are often in the order of twentyfive feet in diameter, and it will be apparent that the mechanical problems of spinning them and of shipping them and of mounting them are not easy to cope with. In the larger sizes, it is customary to weld sheets of aluminum together to make a composite plate and then subsequently, by means of a spinning operation, form the sheet to the shape of a die mounted in a rotatable chuck. This is very cumbersome where large composite sheets are necessary. Moreover a large sized reflector when formed presents a diflicult shipping problem. Mechanical problems are not finished when the reflector reaches its mounting site because in the larger sizes there is mechanical difliculty in supporting the large reflector in an operative position.

This invention relates to a construction for a parabolic communication reflector which minimizes the mechanical problems in constructing, shipping and mounting.

It is an object of this invention to provide a parabolic communication reflector that is easy to construct.

It is a further object of the invention to provide a parabolic communication reflector that is easy to ship.

It is a further object of the invention to provide a parabolic communication reflector that is easy to support in an operative position.

With these and other objects in view, a parabolic communication reflector according to this invention has a smooth parabolic reflecting surface. The parabolic reflecting surface comprises a centre reflecting surface area and an annular reflecting surface area around the centre reflecting surface area, the parabolic reflector comprising a centre reflector sheet member on which the centre reflecting surface area is formed and at least one annular reflector sheet member upon which said marginal reflecting sheet area is formed, said centre reflector member and said annular reflector member being separate and having securing means at their abutting edges to maintain their respective reflecting areas in parabolic relation.

The invention will be clearly understood after reference to the following detailed specification read in conjunction with the drawings.

3,543,278 Patented Nov. 24, 1970 In the drawings,

FIG. 1 is a view of a parabolic reflector according to this invention;

FIG. 2 is a cross-section of the parabolic reflector; and

FIG. 3 is a section along the line 3--3 of FIG. 1.

Referring to the drawings, the numeral 10 refers to a parabolic reflector for use in the communications field. It has a smooth parabolic reflecting surface formed from a sheet of aluminum, usually about one-quarter of an inch thick, and spun against a wooden or like spinning die mounted in a rotatable chuck according to a known technique which is not described in detail in this specification. The parabolic reflecting surface of the reflector is divided into a centre reflecting surface area 12 and a marginal reflecting surface area 14 around the centre reflecting surface area 12. The parabolic reflector is made from a centre reflector sheet member 12 which provides the centre reflecting surface area and an annular reflector member, generally indicated by the numeral 14, composed of a series of four reflector sheet members 14a which provides the annular reflector surface. It will be noted that the centre reflector sheet member 12 is formed with a rearwardly turned flange 16 and the annular reflector member 14 is formed with a rearwardly turned flange 18. These flanges each cooperate with a ring 20, which is formed from an extruded aluminum section. Spaced apart bolts 22 through the ring and flanges join the abutting edges of the centre reflecting member 12 with the edges of the annular reflector member 14.

Parabolic reflectors are often large and diameters of twenty-five feet are not uncommon. In cases where the outside diameter of the reflector as a whole is large, it is very much easier to be able to form the reflecting surface in a centre section and at least one annular section. The centre section 12 can be formed with fewer mechanical spinning problems than if the section were designed to cover the entire reflector because of its smaller size. The annular reflector member 14 is separately spun on a chuck mounted form from an annular disk and, if desired, can be further out radially into sections 14a as shown. Thus, the forming or spinning operation of the aluminum sheet is achieved from smaller pieces of sheet aluminum and the mechanical handling and forming problems in the construction are very much reduced.

The forming of the flanges 16 and 18 at the abutting edges of the centre member and the annular member is done according to standard spinning practice. The flange at the edge of the centre member 12 is formed with a standard radiusing roller and/ or convex roller. The flange at the mating edge of the annular section 14 is preferably formed over the forming die. The flange at the outer extremity of the annular section 14- is formed with a radiusing roller. These are standard techniques. The manner of achieving the flange means for interconnecting the sections or, for that matter, the actual form of the flange means is not part of this invention. The inventive concept is the formation of a reflector that consists of a centre member and annular members for the purposes indicated.

In addition to being easier to construct, the reflector according to this invention can be shipped from its place of manufacture to its place of use in knocked-down form, i.e. with the centre reflector member and the annular reflector member separately packed.

It is possible for shipping purposes to cut the annular member in a radial direction, as indicated by the numeral 15, in order to further reduce its size for shipping. At the site, the member can be rejoined to form it into its parabolic arrangement in the reflector by means of a molding 17 that is bolted to adjacent radially extending edges as illustrated. The joints may be welded as an alternative means of reassembling the annular member.

Once on the site of use, the pieces are assembled as illustrated in the drawing and the ring 20 can be used as a mounting ring to set the reflector on its tower. it will be apparent that ring 20 is in a very strategic support position for supporting the reflector as a whole and that it forms an excellent and stable suport for the reflector that can be very easily mounted onto a tower or the like.

Ring 20 can conveniently be formed by extruding a length of material from aluminum having a cross-section similar to that shown in FIGURE 2. A length of the extruded section is taken, formed into a ring, and welded at its abutting free ends to form the ring member. Ring '20, in addition to strengthening the unit, provides a convenient and inexpensive manner for mounting the reflector on its tower.

Modifications of the invention will be apparent to those skilled in the art. For example, one might dispense with the mounting ring 20 and merely secure the flanged edges of the sections 12 and 14 together to form a composite reflector. In this case, some of the advantage of the construction in mounting might be lost, but the ad- 'vantages of manufacture and shipping over and above the one-piece construction are substantial enough to give this construction substantial advantage over the prior art. Moreover, in some cases the annular reflecting members might be made as one annular ring or more than one annular reflecting member might be used to make up the composite reflecting surface.

Modifications of the invention will be apparent to 4 those skilled in the art and it is not intended that the foregoing description should be read in a limiting sense.

What I claim as my invention is:

1. A reflector having a composite parabolic surface disposed about a parabolic axis and comprising, a central reflector sheet member including a portion of said parabolic surface through which said axis passes, the central member having an outer integral flange extending away from said surface and disposed substantially along said axis; a mounting ring disposed about said axis and having an inner surface mating with said outer flange; peripheral sheet members disposed about said central member, each peripheral member including a marginal portion of said composite parabolic surface and having an inner integral flange extending away from said surface and mating with the outer surface of said ring; and tie means transfixing said inner and outer flanges and said ring.

References Cited UNITED STATES PATENTS 2,786,998 3/1957 Davis 3439l5 2,827,629 3/ 8 Rounsefell 343-912 3,234,550 2/1966 Thomas 343-912 ELI LIBERMAN, Primary Examiner US. Cl. X.'R. 343-916 

